1
ENEGeol 2017 – PART 2
APPLICATIONS OF TEPHROCHRONOLOGY
Volcan Chaiten, 2008
Key References
• Alloway, B.V., Lowe, D.J., Larsen, G.,
Shane, P., and Westgate, J.A.
Tephrochronology In: Encyclopedia of
Quaternary Sciences, 2nd edition (ed.
Scott Elias), Volume 4, 277-304, Elsevier,
Amsterdam. (2013)
• Lowe, D.J., Alloway, B.V.,
Tephrochronology. In: Rink, W.J.,
Thompson, J. (Eds.), Encyclopedia of
Scientific Dating Methods. Springer,
Netherlands, pp. 1-26. (2014)
2
Map of distributions
of Kawakawa/Oruanui
(red dashed line) and
Rerewhakaaitu (blue
dot-dash line)
tephras.
Isopachs in
centimetres.
Applications of Tephrochronology GEOMORPHIC & LANDSCAPE RECONSTRUCTION
Kawakawa Tephra
Howard Valley
Nelson Lakes Taranaki
McKay’s Crossing,
Wellington
3
Section near Putaruru, North Island,
showing Kawakawa/Oruanui tephra
as prominent pinkish-white marker
bed ~0.5 m thick in middle of section
overlying tephric loess and paleosol.
Pale tephra bed near base (by
person) is c. 50,000 cal.-yr old
Rotoehu Ash, which overlies a dark
paleosol on loess.
Summary diagram for the period c. 30,000 to
10,000 14C yr BP in central and southern North
Island, New Zealand
GEOMORPHIC & LANDSCAPE RECONSTRUCTION
Kawakawa Tephra
Close-up photo of core from Lake Rotoroa
(Hamilton, New Zealand) showing darkening
in sediment colour just above c. 17,600 cal.
yr BP Rerewhakaaitu Tephra that reflects an
increase in organic content because of re-
afforestation and amelioration in climate
GEOMORPHIC & LANDSCAPE RECONSTRUCTION
Rerewhakaaitu Tephra
4
Applications of Tephrochronology VOLCANIC HAZARD ASSESSMENT & ERUPTION
FREQUENCY FROM LONG TEPHRA RECORDS Long tephra records can contribute
significantly to an understanding of eruption
frequency and tephra dispersal.
A notable example: Lago Grande di Monticchio in
southern Italy. Here, 340 distal tephra layers are
preserved within 72.5 m of lacustrine sediments
deposited over the last 100,000 years.
Most tephras (n = 313) derived from volcanic eruptions of the
Campanian province, which still represents an area of volcanic risk for
the Naples metropolitan area. Other tephras are related to high-explosive
events of Roman and Sicilian-Aeolian volcanoes (n = 17) or cannot
be correlated with any distinct volcanic source (n = 10).
Synthetic Aperture Radar (SAR) multi-
temporal colour composite image showing
the Bay of Naples which lies in the centre
of the Campanian volcanic province - which
is now flanked by the active Vesuvius &
Phlegrean Fields.
5
Between 27,000 and 9500 cal. yr BP, fallout from 44 eruptions were recorded
in the maars, an average recurrence of c. 400 years.
These comprise events from OVC (1 per 2,200 yrs), TVC (1 per 5,800 yrs), EgVC
(1 per 830 yrs), TgVC (1 per 2,900 yrs) and AVF (1 per 2,900 yrs).
6
A total of 106 different tephra layers
from local and distant volcanoes (>0.5
mm thick) in the last 80 kyr have been
recorded in the Auckland maars, an
average recurrence of ca. 755 yr
(Molloy et al., 2009).
These comprise 52 events from EgVC
(1 per 1.5 kyr), 24 AVF events (1 per
3.5 kyr), 21 Taupo Volcanic Zone
rhyolite (TVC and OVC) events (1 per
3.8 kyr), 7 TgVC events (1 per 11.4
kyr) and 2 TuVC events (1 per 40 kyr).
Unrecognised cryptotephras (<0.5 mm) are also likely to be present in
the cores. Such cryptotephras also potentially have significant
implications for hazard assessments as exemplified by the 1995-1996
eruptions of Ruapehu Volcano.
Applications of Tephrochronology BASIN STUDIES
Precise identification of tephra
layers has also proven to be
important in understanding the
growth and development of
sedimentary basins as well as for
the correlation of glacio-eustatic
sedimentary cycles across marine
basins.
7
Wanganui Basin
Tephra Localities – Wanganui Basin Inset - localities along the Rangitikei River
8
Pakihikura Tephra, c. 1.60 Ma,
late MIS 55 – early MIS 54
Fordell Ash,
c. 0.310 Ma,
MIS 9a
Vinegar Hill Tephra, c. 1.75 Ma,
MIS 61
9
Applications of Tephrochronology HOMINID EVOLUTION
Most of the hominid remains and
associated artefacts from the East
African rift system have been found
in Plio-Pleistocene volcaniclastic
sediments.
An Australopithecus Afarensis was
found at the Afar Depression in Ethiopia
in November, 1973. Lucy was a 3.2 year-
old – only 40% of Lucy's skeleton was
found.
Comparison of radiometric &
stratigraphic (interpolated)
ages for East African tuffs
between 4.0–3.4 Ma and their
orbitally tuned ages derived
from the marine sediment
chronostratigraphy at ODP
sites 721 and 722 in the
Arabian Sea
10
Applications of Tephrochronology ARCHAEOLOGY
Tephrochronology has increasing application in
archaeological studies because they form
isochronous horizons enabling the correlation of
equivalent-aged successions.
Late Bronze Age explosive eruption of Thera
(Santorini) dated c. 1667–1644 BC
Regional distribution
of tephra from the
Thera eruption (shaded
area) in the Late
Bronze Age.
Tephra thickness isopachs are
in centimetres. Symbols
identify sites where tephra has
been identified in cores
(triangles) & at archaeological
sites (squares)
11
Another example where
tephrochronology has advanced
archeological studies is in New
Zealand where a key rhyolitic
eruptive, Kaharoa Tephra (KT), has
helped resolve the controversial
timing of initial Polynesian
settlement.
Summary diagram of 12
bracken (Pteridium) spore
profiles, North Island, New
Zealand, containing the
Kaharoa Tephra settlement
datum (KT). In most profiles,
the deforestation signal
(increase in Pteridium and
charcoal, decline of tall trees)
occurs at around or after the
deposition of KT, but in four
(Kopouatai, Papamoa,
Kohika, Holden’s Bay) it
occurs just before, by
perhaps a few decades.
12
SUMMARY
• Tephras are now routinely detected and dated in terrestrial, marine and ice-core records throughout the world in both macroscopic & microscopic (cryptotephra) forms
• Tephra’s are used in a diverse range of disciplinary fields including stratigraphy, geomorphology, glaciology, sedimentology, archaeology, hominid evolution, and paleoenvironmental reconstruction.
• Tephrochronology is also an essential tool for establishing the frequency/periodicity of volcanic activity and for assessing volcanic hazards.
• Finally, perhaps the most exciting development is the use of tephrochronology, uniquely, to effect more precise correlations between marine, ice-core and terrestrial records.
Key References • deMenocal, P.B. and Brown. F.H. (1999). Pliocene tephra correlations between East African
hominid localities, the Gulf of Aden, and the Arabian Sea. In Hominoid Evolution and Climatic
Change in Europe (J. Agusti, L. Rook and P. Andrews, Eds.) vol. 1, Cambridge University Press.
• Lowe, D.J., Shane, P.A.R., Alloway, B.V., and Newnham, R.M. (2008). Fingerprints and age
models for widespread New Zealand tephra marker beds erupted since 30,000 years ago: a
framework for NZ-INTIMATE. Quaternary Science Reviews 27, 95-126.
• McCoy, F.W. and Heiken, G. (2000). The Late-Bronze Age explosive eruption of Thera (Santorini),
Greece: Regional and local effects. Geological Society of America Special Paper 345, 43-70.
• Molloy, C., Shane, P., and Augustinus, P. (2009). Eruption recurrence rates in a basaltic volcanic
field based on tephra layers in maar sediments: Implications for hazards in the Auckland volcanic
field. GSA Bulletin 121, 1666-1677.
• Newnham, R.M., Lowe, D.J., McGlone, M.S., Wilmshurst, J.M. and Higham, T.F.G. (1998). The
Kaharoa Tephra as a critical datum for earliest human impact in northern New Zealand. Journal of
Archaeological Science 25, 533-544.
• Pillans, B., McGlone, M., Palmer, A., Mildenhall, D., Alloway, B.V., and Berger G. (1993). The Last
Glacial Maxima in central and southern North Island, New Zealand: a paleoenvironmental
reconstruction using the Kawakawa Tephra Formation as a chronostratigraphic marker.
Paleogeography, Paleoclimatology, Paleoecology 101, 283-304.
• Pillans, B., Alloway, B.V., Naish, T., Westgate J.A., Abbot, S., Palmer, A.S. (2005). Silicic tephras
in Pleistocene shallow marine sediments of Wanganui Basin, New Zealand. Journal of the Royal
Society of New Zealand 35, 43-90.
• Wulf, S., Kraml, M., Brauer, A., Keller, J., Negendank, J.F.W. (2004). Tephrochronology of the
100ka lacustrine sediment record of Lago Grande di Monticchio (southern Italy). Quaternary
International 122, 7-30.